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+; "fluidlet.scm", FLUID-LET for Scheme
+; Copyright (c) 1992, Dorai Sitaram (dorai@cs.rice.edu)
+;
+;Permission to copy this software, to redistribute it, and to use it
+;for any purpose is granted, subject to the following restrictions and
+;understandings.
+;
+;1. Any copy made of this software must include this copyright notice
+;in full.
+;
+;2. I have made no warrantee or representation that the operation of
+;this software will be error-free, and I am under no obligation to
+;provide any services, by way of maintenance, update, or otherwise.
+;
+;3. In conjunction with products arising from the use of this
+;material, there shall be no use of my name in any advertising,
+;promotional, or sales literature without prior written consent in
+;each case.
+
+(require 'rev4-optional-procedures)
+(require 'common-list-functions)
+(require 'dynamic-wind)
+(require 'macro)
+
+(define list-set! (lambda (s i v) (set-car! (list-tail s i) v)))
+
+(define-syntax fluid-let
+ (syntax-rules ()
+ ((fluid-let ((x v) ...) . body)
+ (let ((%x-names (list 'x ...))
+ (%x-values (list x ...))
+ (%fluid-x-values (list v ...)))
+ (dynamic-wind
+ (lambda ()
+ (set! x (list-ref %fluid-x-values
+ (comlist:position 'x %x-names)))
+ ...)
+ (lambda () . body)
+ (lambda ()
+ (let ((%x-position (comlist:position 'x %x-names)))
+ (list-set! %fluid-x-values %x-position x)
+ (set! x (list-ref %x-values %x-position)))
+ ...))))))
+
+;--- end of file